Influence of C‐reactive protein levels and age on the value of D‐dimer in diagnosing pulmonary embolism. (22nd November 2013) - Crop, Meindert Johannes
Abstract Background Recently, the number of performed CT‐angiographies to diagnose pulmonary embolism (PE) rised markedly, while the incidence of PE hardly increased. This low yield of CT‐angiography leads to more patients exposed to radiation and higher costs. Aim The diagnostic value of age, C‐reactive protein (CRP) and D‐dimer in PE was investigated. Additionally an age‐adjusted D‐dimer cutoff level [age‐adjusted cutoff = age/100 mg/L] was compared with the conventional cutoff level in diagnosing PE for patients ≥50 yr. Methods This observational study (2004–2007) included all consecutive patients suspected for PE presenting on the emergency department with a performed CT‐angiography after measuring CRP and D‐dimer levels. Results Of 4609 patients suspected for PE, 1164 patients underwent CT‐angiography of whom 309 (26.5%) had PE. Correlation between CRP and D‐dimer was 0.42 (P < 0.001). D‐dimer and age correlated positively (rs = 0.33, P < 0.001), but only in patients >50 yr and independent of PE. Multivariate regression analysis showed significant contribution of age, D‐dimer and age‐adjusted D‐dimer for diagnosing PE, but not for CRP. Using an age‐adjusted D‐dimer cutoff value increased specificity from 37% to 50%, whereas sensitivity declined from 96% to 90%. Applying this age‐adjusted cutoff level in patients ≥70 yr, specificity increased from 18% to 40%, while sensitivity decreased from 96% to 88%. Conclusions In the prediction of PE, age and D‐dimer levels are relevant, while CRP level is not. Using an age‐adjusted D‐dimer cutoff in older patients remarkably improves the specificity of D‐dimer testing with a minor decline in sensitivity. This may increase the yield of CT‐angiography in diagnosing PE.